This invention relates to oil refineries and, more particularly, to a process for refining crude oil and purifying effluent refinery water.
Purified water and processed steam (vaporized water) are used in many oil refinery operations. Such refinery operations include steam injection in pipestills, cokers, fluid catalytic cracking units, mid-distillate strippers, and light distillate strippers and the use of water in heat exchangers and various water-wash operations.
Significant quantities of contaminated, sour refinery water are produced during such oil refinery operations. Sour refinery water is laden with suspended and dissolved impurities, such as phenols, sulfides, ammonia, and other hydrocarbons, such as oil and grease. Oil refinery water usually contains different pollutants than sewage, causing difficult disposal and purification problems.
Sour refinery water needs to be treated for safe effective use in refinery operations as well as for safe discharge into the ocean, lakes, rivers, streams, collection basins and other bodies of water. Sour refinery water also needs to be treated to comply with the standards set by the Federal Environmental Protection Agency and State Regulatory Agencies. Untreated sour refinery water is usually not safe for drinking or bathing. It can be toxic to aquatic life. It also contains sulfides and other contaminants which can corrode and plug refinery equipment.
The quantity of pollutants in oil refinery water is often determined by measuring the amount of dissolved oxygen required to biologically decompose the waste organic matter in the polluted water. This measurement, called biochemical oxygen demand (BOD), provides an index of the organic pollution in the water. Many organic contaminants in oil refinery water are not amenable to conventional biological decomposition. Therefore, tests such as chemical oxygen demand (COD) and total organic carbon (TOC) are used to more accurately measure the quantity of pollutants in oil refinery water. Chemical oxygen demand measures the amount of oxygen needed to chemically oxidize the organic matter in waste water. Total organic carbon measures the amount of organic carbon in waste water.
Over the years, a variety of methods have been developed for purifying or otherwise processing sour refinery water, oil shale retort water, waste water petrochemical streams, and sewage. Typifying the many prior art methods for purifying and/or processing sour refinery water, oil shale retort water, waste water petrochemical streams, and sewage are those described in U.S. Pat. Nos. 1,955,065, 2,073,248, 2,789,083, 2,808,375, 2,812,305, 2,948,677, 2,999,808, 3,123,556, 3,211,643, 3,335,865, 3,589,997, 3,663,435, 3,815,750, 3,836,456, 3,846,293, 3,903,250, 3,904,518, 4,026,791, 4,043,881, 4,049,782, 4,066,538, 4,069,148, 4,073,722, 4,105,546, 4,121,662, 4,124,501, 4,141,824, 4,162,902, 4,178,039, 4,178,824, 4,179,365, 4,207,179, 4,231,617, 4,233,152, 4,289,578, 4,379,591, 4,387,025, 4,401,570, 4,415,442, 4,422,940, 4,499,058, 4,505,813, 4,518,502. These prior art methods have met with varying degrees of success.
It is, therefore, desirable to provide an improved process for treating oil refinery water.